Heat transfer element



April 2, 1935. R. M. GATES HEAT TRANSFER' ELEMENT- Filed May 11, 1933 ATTORNEY Patented Apr. 2, 1935 UNITED STATES 1,996,105 HEAT TRANSFER ELEMENT Robert M. Gates, Scarsdale, N. Y., assignor to The Superheater Company, New York, N. Y.

Application May 11, 1933, Serial No. 670,432

4 Claims.

This invention relates to heat transferring devices and has for its purpose the provision of improved means for enhancing the rate of such transfer. It is illustrated in the accompanying drawing in which Fig. 1 is a cross-sectional view on line l-I of Fig. 2 showing a pipe equipped with my invention. Fig. 2 is an elevation of a portion of such a pipe. Fig. 3 is a view similar to that of Fig. 2 illustrating a modification and Figs. 4 and 5 are views at right angles respectively of Figs. 2 and 3.

The value of increasing the external heat absorbing or heat delivering surface of pipes when these pipes are used for certain purposes is well understood. Such an increase of the external surface is beneficial when the medium coming in contact with the external side of the pipe delivers or absorbs heat at a slower rate per unit of area than the medium flowing through the pipe. This is a common situation and exists for example in the case of economizers heating feed water for boilers where the gases coming in contact with the outer surface cannot deliver heat at the same rate per unit area to the pipe as the water is capable of absorbing on the inside.

A common means for enhancing the rate of heat transfer under such conditions is the provision of external fins or ribs. Circumferentially extending ribs are difiicult to apply in such a manner that the heat transfer from them to the pipe is satisfactory. Longitudinally extending fins have been applied with more or less success by welding them to the pipes. Certain disadvantages, however, are encountered in such practice. In spite of giving such fins as favorable a shape as possible, the outer edge will or- -dinarily become considerably hotter than the edge connected to the pipe and'this results in distorting the pipe or at times in rupturing the 40 connection of the fin with, the pipe. My invention, while retaining all the advantages of such 'a fin, removes the drawbacks referred to and in addition provides further advantages.

The pipe I, shown by way of illustration in the drawing, has welded to it, preferably on diametrically opposite sides, two structures.22 shaped in accordance with my inventive idea. Each of these structures comprises a longitudinally extending strip 3 from which extend out- V5 wardly pegs or pins 4-4 which are advantagerounded, but the shape may be widely varied. The forms shown are designed to offer a minimum of resistance to gas fiow where such flow occurs between the pegs.

Such a strip equipped with such pegs can 5 readily be made by means which it is unnecessary to illustrate from a strip of metal. The

specific way in which this is done forms no part of the present invention and is therefore not described in detail herein. It may be 'mentioned, however, that the preferred way is by drop forging. The length of the pegs 4 depends somewhat on circumstances. will be clear that for a given length of these pegs a greater total heat absorbing surface is presented by my construction than is present' 'in a fin of the same depth made according to the usual practice. The disadvantage pointed out above in connection with fins that the outer edges by their greater expansion from their higher temperature cause the pipes to warp is eliminated by my construction. The outer ends welding is shown particularly at 5-5 in Fig. 1.

It is necessary, as is also the case in the usual form of fins, to make a good and suincient heat transferring bond between the heat absorbing structure and the pipe but this is merely in'ac-. cordance with ordinary good practice.

In practice it will be of advantage usually to taper the pegs or pins somewhat toward the outer end at least in one direction and this is illustrated in Figs. 3 and 51 Here the dimension at right angles to the axis of the pipe is left the same throughout but the dimension in the direction parallel to the axis of the pipe is decreased toward the outer end of the pins. If desired, the pins could be tapered with respect not only to the dimension parallel to the pipe, but also to the dimension at right angles to it, although this is not usually of any great advantage.

The strip need not be continuous from one end of the pipe to the other, but may obviously be made in several lengths if desired.

Depending on the use to which the pipe is to In any event, it i be put, strips of this sort may be placed at two or more points circumferentially of the pipe. In the usual situation there will be two strips at diametrically opposite points.

The forms of the invention described above are of course only illustrative and variations can readily be made in practice without losing theadvantages of the invention.

What I claim is:

1. In apparatus of the class described, the combination of a pipe, a fin welded to the exterior of thepipe along a line parallel to its axis and comprising a strip relatively thin in a radial direction and in contact with the pipe and pins unitary with it and extending in a direction away from the pipe, the pins being generally oval in crosssection with the long dimension of the oval transverse to the fin.

2. In apparatus of the class described, the combination of a pipe, a plurality of fins welded to the exterior of the pipe along circumferentially spaced lines parallel to the axis of the pipe, each fin comprising a strip relatively thin in a radial 7 direction and in contact with the pipe and pins unitary with it and extending in a direction away fromthe pipe, the pins being generally oval in cross-section with the long dimension of the oval transverse to the fin.

3. The combination set forth in claim 1, the fins being two in number and diametrically opposite each other, the pins being tapered toward their outer ends.

4. In apparatus of the class described, the combination of a pipe for heat transfer to or from a fluid moving transversely to its axis, a fin welded to the exterior of the pipe along a line parallel to its axis and in a diametrical plane at right angles to the flow of thefluid and comprising a strip relatively thin in a radial direction and verse to the fin, whereby stresses within the fin due to difierential expansion of the parts near the pipe and those remote from the pipe are minimized and the resistance to flow of the fluid between the pins. is reduced.

ROBERT M. GATES. 25 

